Diclofenac + Nabumetone

The combination of diclofenac and nabumetone is used primarily for treating rheumatoid arthritis (RA) and osteoarthritis, particularly in patients with severe arthritic pain who have insufficient control with single-agent therapy[1][5]. This combination leverages a unique pharmacological interaction where nabumetone's active metabolite (6-MNA) inhibits the protein binding of diclofenac, thereby increasing its free concentration and enhancing its analgesic effect[1][5]. ## Mechanism of Action Diclofenac and nabumetone are both non-steroidal anti-inflammatory drugs (NSAIDs) that work by inhibiting cyclooxygenase (COX) enzymes: - **Diclofenac** inhibits both COX-1 and COX-2 enzymes, reducing the production of prostaglandins that mediate pain and inflammation[2]. It's commonly used in suppository form for patients with severe arthritic pain. - **Nabumetone** is a prodrug that is metabolized in the liver to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA), which also inhibits COX-1 and COX-2 with some selectivity toward COX-2[3]. The combination therapy works through a unique mechanism where 6-MNA (nabumetone's active metabolite) inhibits the protein binding of diclofenac[1]. Since diclofenac has a high binding percentage to serum proteins, this inhibition temporarily increases the free concentration of diclofenac in the bloodstream, enhancing its analgesic effect[1][5]. ## Clinical Use This combination is particularly beneficial for rheumatoid arthritis patients with severe arthritic pain who don't achieve adequate relief with standard therapy[1][5]. Studies have shown that when nabumetone is added to diclofenac therapy, patients experience improved pain relief compared to diclofenac alone[1][5]. In clinical practice, the combination might involve: - Diclofenac suppository (typically 12.5-50 mg daily) - Nabumetone tablet (typically 800 mg daily)[5] ## Dosing While specific combination dosing varies based on individual patient needs, typical dosages from the research include: - **Diclofenac**: 12.5-50 mg daily (often as a suppository)[5] - **Nabumetone**: 800 mg daily (oral tablet)[5] For nabumetone alone, standard dosing is: - Initial dose: 1000 mg orally once daily - Maintenance dose: 1500-2000 mg orally per day in 1-2 divided doses